IgGs, high-abundance proteins

The IgG purification procedure is repeated in order to ensure exclusive isolation of IgG from patient sera. We have found that with only one purification run, high-abundance proteins other than IgG may be present in the eluted solution. 

This approaeh was suggested and adopted by two groups of researehers (Steel et ah, 2001 Poon and Johnson, 2001). However, one of the problems of this method is due to the presence of a few highly abundant proteins such as albumin, transferrin, and immunoglobulin G (IgG) in the serum proteome profile, which may distort the separation and/or mask the minor proteins present. Thus selective removal of these proteins, especially albumin (representing 30-50% of the total serum protein) is recommended prior to Ifactionation by 2-DE. In many cases, the differences in the protein of interest in the serum protein profile may be due to post-translational modifications, especially glycosylation. In fact, different glycosylated forms of AFP were detected in the sera of HCC patients (Johnson et ah, 1999). 

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